The Senate was due to start its own voting process on Wednesday, with a majority expected to vote for Rousseff to be suspended. It was not clear whether Maranhao's order would stand or would be challenged, possibly in the Supreme Court.

In her first reaction, Rousseff interrupted a speech to supporters to say that she'd just got unconfirmed news of her impeachment hitting a roadblock.

Brazil street protests demand removal of Dilma Rousseff from power

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"I don't know the consequences. Please be cautious," she said, calling on her backers to "defend democracy."

The lower house voted in mid-April by an overwhelming majority to send Rousseff's case to the Senate for trial. She is accused of illegally manipulating government budget accounts during her 2014 reelection battle but says that the process has been twisted into a coup d'etat.